An engine, for example, an internal combustion engine for a vehicle, outputs exhaust during operation. The exhaust emitted from the engine may include gas (such as NOx, SOx, CO2), water (including water vapor and/or condensed water droplets), particulates, etc. Particulates can be solid and/or liquid, and may include carbon and/or sulfuric acid, which are by-products of the combusted fuel, and may include hydrocarbons that are by-products of combusted fuel and/or burned lubricant.